A Hormonal Network Dedicated to Maintaining Weight
A number of other hormones effect whether a person feels hungry or full at any particular time of the day. Cholecystokinin (CCK), peptide YY (PYY), amylin, and glucagon-like peptide-1 (GLP-1) are hormones that are secreted by the gastrointestinal tract and pancreas in response to a meal and act on the brain to suppress appetite. A different hormone, ghrelin, is secreted from the stomach when it is empty, and causes hunger. Many of these hormones have been shown to interact with leptin and with each other, and so for example high levels of leptin plus amylin may cause more satiety than high levels of either hormone alone.
What happens to all of these weight-related hormones when a person loses weight? That question was recently answered in an important study conducted by a group of Australian researchers lead by Dr. Priya Sumithran that was published in the October 27 issue of the New England Journal of Medicine. The researchers recruited overweight people and put them on a strict diet (500 to 550 calories a day) that caused them to lose at least 10% of their body weight and kept them on a diet that would maintain the weight loss for one year. At the end of the year, the participants had significant changes in their obesity-related hormones. For example, leptin levels had fallen by about two-thirds when the subjects initially lost weight, and were still one-third lower at the end of the one-year study period even though participants had regained much of the lost weight. Other obesity-related hormones including those listed in the chart above were also changed. Going along with changes in hormone levels, participants were also found to have increased appetite and decreased metabolism. These results suggest that multiple hormones change in response to weight loss and they continue to encourage weight regain for at least a year after a person has lost weight.
|Hormone||Source||Weight Effect Overview||Approved Medications Mimicking Hormone|
|Leptin||Fat Cells||Long-term regulator of weight, opposes weight change|
|GLP-1 (Glucagon-Like Peptide-1)||Gut||Suppresses appetite following a meal||Byetta/Bydureon (exenatide), Victoza (liraglutide)|
|Amylin||Pancreas||Suppresses appetite following a meal||Symlin (pramlintide)|
|PYY (Peptide YY)||Gut||Suppresses appetite following a meal|
|Cholecystokinin (CCK)||Gut||Suppresses appetite following a meal|
|Ghrelin||Stomach||Causes hunger and promotes energy storage in fat|
Taken together, all of this scientific evidence creates a compelling story of why weight loss is so challenging for most people. When weight is lost, multiple hormones controlling hunger and metabolism work together to cause weight regain. The greater the weight loss, the greater the hunger and the lower the metabolism, and unfortunately for most dieters the urge to eat eventually trumps a conscious desire to be thin.
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NOTE: This information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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